Tiny Dinosaurs Left Footprints On Ancient South Pole

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Several groups of dinosaurs that were roaming the South Pole more
than 100 million years ago left three-toed prints in the wet,
sandy soil. As they became compacted into cliffs, the prints
waited patiently for Anthony Martin of Emory University to
stumble across them in what is now Victoria, Australia. He found
24 complete prints.

"This is a big deal, as they represent the greatest number of
polar dinosaur tracks found in any one place in the Southern
Hemisphere," Martin wrote on his blog, The Great Cretaceous
Walk. "It’s enough to make you want to do a happy dance."

Tiny theropods

The tracks pulled from the sandstone blocks were prints from
theropods — bipedal, mostly carnivorous dinosaurs
related to modern birds. The tracks indicated that the
theropods were of three different sizes, ranging from the size of
a chicken to around the size of a crane.

Because of their size and bones found in other sites in Victoria,
the researchers are fairly confident they belong to a group of
theropods called ornithomimosaurs, also known as "ostrich mimics"
because their anatomy is similar to that of modern large
flightless birds.

The printed slabs of sandstone were found along the rocky and
remote Milanesia Beach in Otways National Park, west of
Melbourne. The rough surf pounds the coastal cliffs, frequently
fracturing slabs off the cliff face. When the tracks were made,
Australia was connected to Antarctia and was located much closer
to the South Pole, as a part of the paleogeographic continent of
Gondwana. [ Photos
of the dinosaur tracks ]

Martin set off on the trail toward the footprints among the
ragged slabs scattering the shore after he noticed ripple marks
and trace fossils of insect burrows. "The ripples and burrows
indicate a floodplain, which is the most likely area to find
polar dinosaur tracks," he explained.

Researchers cannot determine the species of the theropods from
the tracks. It's possible they were all of the same species
(possibly
even a theropod family ), or they could have been different
species traveling in the same area at roughly the same time.

When the tracks were laid down between 115 million to 105 million
years ago, Earth was experiencing global warming, with the
average temperature of the area at 68 degrees Fahrenheit (20
degrees Celsius) — about 10 F (6 C) higher than current
temperatures there.

This would have dramatically affected the planet's biology and
ecology. "These tracks provide us with a direct indicator of how
these dinosaurs were
interacting with the polar ecosystems during an important
time in geological history," Martin said in a statement.

The report of the footprints was published online Aug. 9 in the
journal Alcheringa.

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